What is Today I Learned (TIL)?

Today I Learned, abbreviated TIL, is an online acronym used in post titles and messages to introduce a surprising fact the poster just discovered.

Where did Today I Learned (TIL) come from?

The phrase started showing up on Reddit and Digg around April 2007, and Redditor nix0n founded the /r/TIL subreddit on December 28th, 2008.

What does Today I Learned (TIL) mean?

TIL stands for "today I learned," a shorthand way of saying the poster just picked up the fact they are about to share.

How do you use Today I Learned (TIL)?

You typically write "TIL that…" at the start of a post or message, followed by the fact and, on Reddit, a link to a reputable source.

Is Today I Learned (TIL) still popular?

The /r/TodayILearned subreddit was already near 10 million subscribers by January 2016 and is one of Reddit's long-running default-tier communities.

Today I Learned (TIL)

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Published October 3, 2026

Today I Learned, or TIL, is an online acronym Redditors and other posters tack onto the title of a thread when sharing a surprising fact they just picked up. The phrase started leaking into social news sites around April 2007, and Redditor nix0n codified it with the /r/TIL subreddit on December 28th, 2008, which grew into one of Reddit's largest trivia communities.

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Overview

Today I Learned is deployed as a title prefix: a poster writes "TIL that…" and then drops a fact that caught them off guard, usually with a link to a source backing it up3. The convention on /r/TodayILearned is that the fact has to be something the user genuinely just stumbled across, not trivia they went hunting for, which distinguishes TIL from a general "did you know" post3.

The acronym functions as a politeness marker as much as a signpost. By leading with TIL, posters flag that they are not claiming expertise, they are passing along something new to them, which lowers the bar for sharing offbeat historical, scientific, or pop-culture facts. The Urban Dictionary entry filed in August 2009 by user zBriGuy pinned down the exact meaning as the catchphrase moved out of Reddit threads and into chat and social feeds2. Over time, mods tightened sourcing rules on /r/TodayILearned so that each TIL claim had to link to a reputable write-up, which pushed the format toward verifiable trivia rather than hearsay3.

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Origin & Background

Platform

Reddit / Digg (early use); /r/TodayILearned (viral spread)

Date

2007

The three-letter version of "today I learned" has no single confirmed inventor. Google Trends data cited by Know Your Meme places the phrase's rise on social news aggregators Reddit and Digg around April 2007, before any dedicated community existed for it3. The format was pinned down on December 28th, 2008, when Redditor nix0n created /r/TIL as a place for users to share interesting and specific facts they had just come across, rather than general knowledge they had searched for on purpose3. On August 20th, 2009, Urban Dictionary user zBriGuy filed the earliest known acronymic definition for TIL, describing it as shorthand for "today I learned," the earliest archival timestamp for the acronym itself2.

How It Spread

After /r/TIL went live at the end of 2008, the subreddit snowballed through Reddit's front-page system, which pushed the top-voted facts in front of users who had never visited the community3. By January 2016, the subreddit was closing in on 10 million subscribers, with seven posts clearing the 10,000-upvote mark3.

The brand spread onto other platforms in the early 2010s. An official Twitter feed for /r/TIL went live in February 2010, a Tumblr blog followed in June 2012, and the official Facebook page launched in August 20123. In mid-May 2011, moderators announced that the /r/TIL URL would be retired and that users should switch to /r/TodayILearned, folding the acronym back into the full phrase for the community's canonical name1.

The Urban Dictionary entry from 2009 helped carry the acronym past Reddit, giving casual users a quick explainer when TIL showed up in their feeds2. By the mid-2010s, TIL was common shorthand across Twitter and chat clients for any surprising fact, well beyond the Reddit audience it started with.

Timeline

2007-04

The phrase "today I learned" starts showing up on Reddit and Digg, per Google Trends data[3].

2008-12-28

Redditor nix0n founds /r/TIL as a space for spontaneous trivia posts[3].

2009-08-20

Urban Dictionary user zBriGuy files the earliest known acronymic definition for TIL[2].

2010-02

The official Twitter feed for /r/TIL launches[3].

2011-05

Mods announce /r/TIL will be phased out in favor of /r/TodayILearned as the subreddit's canonical name[1].

2012-06

The official Tumblr blog for TIL launches[3].

2012-08

The official Facebook page launches[3].

2016-01

/r/TodayILearned nears 10 million subscribers, with seven posts past 10,000 upvotes[3].

How to Use This Meme

The common convention is to write "TIL" or "TIL that" at the start of a post title, followed by the specific fact and often a link to a source. Posts on /r/TodayILearned typically focus on narrow trivia (dates, biographies, odd historical footnotes) rather than broad facts, and submissions without a credible source tend to get removed by moderators3. Outside Reddit, people drop TIL into tweets, Discord messages, and chat replies to flag a quick fact without claiming to be an expert on it2.